An integrated optical add-drop multiplexer (OADM), based on a symmetric coupler with a superimposed innovative grating, is proposed. The device has, theoretically, no backreflection at the input and add ports, and does not require a critical positioning of the grating, thus simplifying device fabrication and allowing thermal tuning. Simulations for a glass-on-silica technology show the excellent performances of the proposed device, and the analysis of the sensitivity highlights the specifications that have to be met in the fabrication tolerance